What the Anesthesiologist Should Know before the Operative Procedure

Procedures performed in the electrophysiology lab (EP) include studies of the heart's conduction system, radiofrequency modification and ablation of electrical pathways, and implantation of mechanical devices designed to modify and/or treat various arrhythmias. This chapter deals with anesthetic support of device implantation, in particular pacemakers and defibrillators.

Indications for pacemaker placement follow criteria established by the American Heart Association (AHA), the American College of Cardiology (ACC), and the Heart Rhythm Society (HRS). These include acquired atrioventricular (AV) block (age-related, procedure-related, congenital complete heart block, sinus node dysfunction, neurogenic syncope, or carotid sinus hypersensitivity. Also, cardiac resynchronization therapy (CRT) can be delivered via pacemaker to patients with drug-refractory heart failure in an effort to improve hemodynamics. CRT is indicated in patients with an EF less than 35%, QRS >120 msed, or NYHA Class III heart failure. Other indications for pacemaker placement may include arrhythmias secondary to other diseases such as neuromuscular disorders, OSA, and bradycardia in heart transplant patients.

Indications for ICD placement include secondary prevention of VT or VF if the arrhythmia is likely to recur despite other therapy. In addition, ICD implantation is indicated for primary prevention in high-risk patients who may not have experienced VT or VF but are high risk by virtue of their heart failure class (>/= 2) or LVEF </=30%-35%. Most (80%) ICDs are implanted for primary prevention. ICDs are also implanted to provide CRT,

In general, the comorbidities of patients who commonly undergo the implantation of these devices are of a broad spectrum. They include extremes of age, history of cardiac disease, low cardiac output states with the accompanying poor perfusion of multiple organs, and neuromuscular diseases. It is important to evaluate each patient's particular comorbidities and anesthetic requirements as is necessary for any other procedure.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Some arrhythmias can be the source of cardiovascular collapse. Transcutaneous and temporary pacing, as well as emergent defibrillation, can serve as a bridge to permanent device implantation that is appropriate once the patient is stable enough to undergo the procedure.

Emergent: In the event of emergent need for pacing or cardioversion from an unstable rhythm, appropriate personnel should be called, defibrillator pads should be placed on the patient, and cardioversion, transcutaneous pacing, and appropriate medications should be administered according to ACLS guidelines.

Urgent: Temporary pacing wires can be inserted at bedside for those patients who need urgent, but not emergent, pacing.

Elective: The patient should only undergo elective placement of a permanent device if they are stable enough for the procedure and anesthesia (if required).

2. Preoperative evaluation

Most of the target patient population suffers from arrhythmias and/or CHF. It is important to identify the underlying etiology of the rhythm abnormality and the anesthetic implications for the primary disease (i.e., pacemaker/ICD placement for ischemic cardiomyopathy). Obesity and sleep apnea are not uncommon in this population, as are all of the hypoperfusion states associated with low cardiac output.

The anesthesia provider should perform a thorough preoperative cardiac assessment, with a particular emphasis on CHF sequelae. The ECG and echocardiography should be reviewed. Other preoperative conditions are discussed below by system.

Delaying surgery may be indicated if: the patient is too unstable to undergo transport to the EP lab. Anesthesia away from the main OR can be risky and testing the device may be unwise if the patient's airway is unsecured or suboptimal or the patient is unable to tolerate induced arrhythmias from a cardiac standpoint.

3. What are the implications of co-existing disease on perioperative care?

Preoperative evaluations should take place as it would for any other anesthetic. Patients should be evaluated by system with particular focus on airway characteristics and cardiac function.

Perioperative risk reduction strategies: No modification of medications is necessary. The patient should be NPO for 8 hours prior to the procedure.

b. Cardiovascular system

CHF, CAD, arrhythmias, congenital heart disease

Acute/unstable conditions: CAD/MI, CHF, unstable arrhythmias

Baseline coronary artery disease or cardiac dysfunction - Goals of management: almost all patients have coexisting cardiac disease. It is important to be aware of these conditions and to optimize them before electively going to the EP lab.

Neuromuscular diseases: Err on the side of reassurance and minimal medication for these patients as the risks of complications from sedatives and general anesthesia usually outweigh the benefits for these relatively short procedures.

Acute issues: see above

Chronic disease: see above.

f. Endocrine:

Diabetes, obesity, thyroid disease, and other metabolic syndromes

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

N/A

4. What are the patient's medications and how should they be managed in the perioperative period?

Patients may be taking a wide variety of medications for management of arrhythmias, CHF, CAD, and other comorbidities mentioned above. Patients may also be taking anticoagulants for arrhythmias and low ejection states. Patients should continue their chronic medications for their cardiac conditions based on a conversation between their cardiologist and the proceduralist (who may be the same person).

All other chronic medications should be managed as they would be for a generic GA.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Chronic antiarrhythmia medications and anticoagulation medications should be managed by the patient's cardiologist and the proceduralist. In general, device implantations are done with the patient's INR between 2-2.5, although recent publications argue that there is no increase in undesired outcome up to an INR of 3.

i. What should be recommended with regard to continuation of medications taken chronically?

N/A

j. How To modify care for patients with known allergies -

Anticoagulation may be required during these procedures. Be aware of patients with heparin-induced thrombocytopenia (HIT) as these patients likely have been exposed to heparin multiple times and are at high risk of developing HIT. Other anticoagulants that may not be as readily reversible and have longer half-lives than heparin may need to be administered. It is important for the entire team to communicate and develop a plan before starting the case.

Standard latex precautions for those with latex allergies should be taken.

l. Does the patient have any antibiotic allergies? (common antibiotic allergies and alternative antibiotics)

Consult with the proceduralist regarding what antibiotic coverage is needed and pertinent antibiotic allergies

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia

Documented: Avoid all trigger agents such as succinylcholine and inhalational agents:

Proposed general anesthetic plan: TIVA for a GA or sedation

Ensure MH cart available: It is important to note if the procedure is being performed out of the main OR

Family history or risk factors for MH: It is probably best to avoid all MH trigger agents given that the patient is likely far from the MH cart and other anesthesia providers.

Local anesthetics/muscle relaxants: These agents should be avoided if the patient is allergic to them.

5. What laboratory tests should be obtained and has everything been reviewed?

Standard laboratory tests for patients undergoing GA should be ordered according to ASA guidelines.

Common laboratory normal values will be same for all procedures, with a difference by age and gender.

Hemoglobin levels: Should be noted for oxygen delivery and bleeding potential.

Electrolytes: K+ and Mg++ are especially important to note if patient is arrhythmogenic.

Coagulation panel: Important to note if patient is to be anticoagulated.

Imaging: Chest radiographs and CT scans can provide information on cardiac status, as well as preexisting pericardial effusions, pulmonary infiltrates, and anatomic locations of previously implanted hardware. Echocardiography should also be reviewed.

Thyroid function tests and, in particular, TSH should be noted.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

As with any surgery, the anesthetic plan in the EP lab will depend on the procedure and the patient. The two most common strategies are GA or IV sedation/MAC. Patients generally do well with local infiltration and moderate sedation during device implantation. For defibrillation threshold (DFT) testing or cardioversion, GA is required.

a. Regional anesthesia

It is unlikely regional anesthesia will play an important role in the EP lab.

b. General Anesthesia

Benefits: A secured airway and motionless patient can free the anesthesiologist and provide good working conditions for the cardiologist. Controlling ventilation for breath holding during crucial portions of the procedure can also be useful.

Drawbacks: A patient with unstable hemodynamics or an unstable rhythm may not tolerate induction or GA well.

Other issues: It is important to note that pacemakers and ICDs are usually placed in an EP lab. This procedure is not normally part of the main OR repertoire. Performing a GA in an unfamiliar environment may be difficult. There are typically physical limitations (small spaces, little room for anesthesia machine), cultural obstacles (procedural team that is unfamiliar with anesthesia and anesthesia providers), and unfamiliar equipment/images (fluoroscopic images with different reference point, moving portions of the imaging system). It is prudent to communicate your needs/concerns with the team before induction of anesthesia.

Airway concerns: Again, this procedure is typically performed out of the OR. There may be limited/no access to help from other anesthesia providers for airway security. Also, the proceduralist in most cases is a cardiologist who is not surgically trained and likely cannot secure a surgical airway in an emergency.

c. Monitored Anesthesia Care

Benefits: Often these patients are hemodynamically unstable and have coexisting pulmonary disease. It may be useful to minimize the amount of anesthetic used. It may also be advantageous to communicate with the patient at certain times throughout the procedure.

Drawbacks: The patient may move, may need airway intervention or attention from the anesthesiologist that may distract from other aspects of care.

6. What is the author's preferred method of anesthesia technique and why?

a. The plan should be for the specific procedure and the individual patient. Clearly, the anesthetic plan should be discussed before the procedure. The anesthesia provider should always be prepared for conversion to GA. In addition to standard ASA monitors, an arterial line should be considered and defibrillator pads should be placed. In most cases TEE will not be needed, but it should always be considered. The anesthesia provider should be involved in the flow of the case and should wear a headset if used by the rest of the team. If GA is performed, paralysis may or may not be desired.

During pacemaker or ICD lead placement testing it is important to ensure that the diaphragm is not paced so neuromuscular blockade is undesirable. This may create a problem when patients with tenuous hemodynamics are implanted. One option is to use partial paralysis during the case, maintaining as much twitch as possible. If an arrhythmia is to be induced, medications with antiarrhythmic properties should be avoided (i.e., lidocaine before induction with propofol, sympathetic and parasympathetic modulating agents).Sometimes gaining access for lead placement can be long and painful. The anesthesia provider can administer opioids and benzodiazepines as well as provide reassurance to the patient. The anesthesiologist should be vigilant during this time as leads can cause arrhythmias and inadvertent pneumothorax can occur.

b. During ICD placement, defibrillation threshold testing (DFT) is often needed. General anesthesia is required during this crucial point of the procedure. Occasionally patients cannot be defibrillated through their device either because the threshold is too high or the lead is incorrectly placed. Infrequently the ICD box itself can be defective. This requires external defibrillation via pads. Complications encountered during DFT include TIA/CVA, cardiopulmonary arrest, PEA, cardiogenic shock, seizures, embolic events, and death. DFT is omitted in unstable patients or patients with untreated CAD.

All complications: see above.

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

There are no special criteria for extubation. However, it should be noted that another provider with airway expertise may not be immediately available. It is advisable to be conservative with patients with difficult airways that may require re-intubation.

c. Postoperative management

What analgesic modalities can I implement?

These procedures are typically not very painful and the use of opioids must be weighed against the possibility of cardiovascular instability and respiratory distress. Toradol IV and other NSAIDs are useful.

All patients receiving an anesthetic must go to the PACU. Most patients should be on telemetry after a device has been placed. It may be necessary to leave the patient intubated. It is advisable to know the staffing for the PACU/ICU. Outside of the main OR it may be difficult to communicate with the PACU or to reserve an ICU bed, and it is not ideal to remain intubated in the EP lab after the procedure is finished. Telemetry is a reasonable option for patients who have undergone either PPM or ICD implantation

What are common postoperative complications, and ways to prevent and treat them?